Soluble complexes between chenopodins and alginate/chitosan: Intermolecular interactions and structural-physicochemical properties

The research aim was to study the nature of intermolecular interactions involved in the formation of soluble complexes between chenopodins (QP) and anionic/cationic polysaccharides, sodium alginate (Alg) and chitosan (CH), above the pI of QP at different protein-polysaccharide ratios; and to evaluate their structural-physico-chemical properties. The interactions and properties analysed by electrical conductivity, zeta potential, hydrodynamic particle size, intrinsic and extrinsic fluorescence spectroscopy, circular dichroism spectroscopy, differential scanning calorimetry and infrared spectroscopy. The protein-polysaccharide ratio and the type of polysaccharide influenced the complexes properties. In QP-CH complexes, the main interactions were electrostatic, while in QP-Alg complexes, hydrophobic interactions, hydrogen bonds and weak electrostatic interactions were detected. Changes in secondary and tertiary structure and increased thermal stability of chenopodins in the presence of both polysaccharides were observed. QP-Alg and QP-CH complexes seemed to have achieved the strongest interactions at 1:4, 2:3 and 3:2 ratios and at 1:4 and 2:3 ratios, respectively.